The present invention pertains to a device for controlling a breathing gas flow, with the device containing a breathing gas block with a cover enclosing a breathing gas space, as well as a heating device for the breathing gas space.
A device for controlling the breathing gas flow, with a breathing gas block, a cover and a valve plate accommodated in a sandwich-like manner between the breathing gas block and the cover, has become known from DE 36 29 353 C1. The breathing gas, with which a patient is respirated, flows through the breathing gas block in various channels. The channels are open toward the valve plate and are able to be closed or released by means of closing elements, which are arranged at the valve plate. The closing elements are actuated pneumatically from the cover by a corresponding control pressure being admitted to individual control pressure spaces, which are associated with the closing elements.
The breathing gas circulating in a breathing circuit is normally enriched with water vapor up to the saturation limit during the return of the expired breathing gas, as a result of which condensation of water vapor may take place in the breathing gas block, but also on the side of the valve plate facing the breathing gas block. To prevent such condensation effects, the material of the breathing gas block is designed in the prior-art device as an electrically conductive heating device and is uniformly heated in all areas by a current flowing through. It was found that the condensate formation within the breathing gas block is subject to very great variations and it is only insufficiently possible to respond to it with a uniform heating of the breathing gas block. To also prevent condensation in the area of problematic condensate traps, the breathing gas block would have to be heated at about 40xc2x0 C. However, such surface temperatures are not acceptable for functional reasons. In addition, a not inconsiderable heat output is also necessary to maintain the entire breathing gas block at this temperature, especially because part of the heat is again removed by heat conduction by adjacent components, e.g., a respiration pump.
The basic object of the present invention is to improve a device of this type such that condensation effects are prevented from occurring with a supply of the smallest possible amount of energy.
According to the invention, a device for controlling the breathing gas flow is provided with a breathing gas block with a cover, which enclose a breathing gas space. A heating device for the breathing gas space is provided. A heating foil is provided as the heating element.
The advantage of the present invention is essentially that condensation can be effectively prevented from occurring by the heating device being designed as one or more heating foils, which are fastened within the breathing gas space enclosed by the breathing gas block and the cover at the points at which the heat output is needed. The heating foil may be applied flatly at the points that are especially susceptible to the condensation of water vapor, as a result of which the heat output supplied can be metered better. It is also possible to supply different heat outputs via the heating foils, so that problem zones can be heated more intensely than other areas, in which only a small amount of condensate is formed, without excessively high surface temperatures developing on the outside of the breathing gas block and the cover.
The heating foils may also be arranged such that they can line breathing gas-carrying channels.
Heating foils preferably consist of a flexible carrier material, in which heating wires are embedded in a meandering manner. However, it is also possible to design the heating foil as a flat resistor element in order to achieve a more uniform distribution of the heat or to apply heating elements in the form of a coating, corresponding to a printed circuit board, to the carrier material.
It is especially advantageous to integrate at least one temperature sensor in the heating foil in order to determine the heating temperature directly at the site of the heating foil. It is especially expedient to arrange more than one temperature sensor on the heating foil to make it possible to measure temperature mean values, on the one hand, and, on the other hand, to be also able to continue to operate the heating foil when a temperature sensor fails. It is also possible to use one of the temperature sensors for the temperature regulation and the other temperature sensor as a pure temperature monitoring sensor.
It is especially advantageous to arrange the heating foil directly at a valve plate, which is located between the breathing gas block and the cover. Since the valve plate partially covers breathing gas channels of the breathing gas block, problematic breathing gas channels can be effectively heated via the valve plate. If the valve plate consists of metal, there is good thermal conduction within the valve plate, so that a single heating foil is normally sufficient to heat the valve plate.
It is especially advantageous to insert the heating foil into an opening located at the valve plate and to seal it with a sealing compound. By sealing in the heating foil, damage that could occur, e.g., during sterilization or the processing is prevented from occurring. The arrangement of the heating foil in the area of the valve plate is especially advantageous also because only the valve plate must be replaced in case of a defect of the heating foil.
It is advantageous to connect the heating point electrically to a control unit via detachable contact means. The control unit processes the measured temperature values and regulates the current flowing through the heating foil corresponding to a preset set point for the temperature. The contacting is preferably performed by means of gold-plated, spring-loaded contact pins, which are electrically connected to corresponding contact surfaces on the heating foil. The contact surfaces have replaceable contact screws, so that contacts can also be replaced individually, without the entire valve plate together with the heating foil having to be replaced.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which a preferred embodiment of the invention is illustrated.